Compressible and flexible fire-resistant seals are used in aircraft engines to maintain an effective heat and flame barrier in areas where there is relative movement between the aircraft engine nacelle and the engine support structure. Conventional seals are typically constructed of preformed elastomer sections with fabric protective covering. Because such materials are not fire resistant, prior seals have required overlapping metal flame shields to insure the seal's ability to contain fire in the designated zone. One prior art seal/shield configuration is shown in FIG. 1. FIG. 1 shows a fire seal 1, comprised of a core formed of an elastomeric material 3 and a fabric protective covering 5 compressed between a pair of flame shield members 7 and 9. In use, one of the flame shield members is attached to an aircraft engine frame and the other is attached to an airframe support structure.
The seal/shield configuration illustrated in FIG. 1 and described above is unsuitable for use on advanced technology prop fan engines because the structure for attaching these new engines to an airframe is designed to permit large deflections between the engine and the airframe in order to isolate continuous low-frequency vibrations. These deflections may be up to three inches compared to deflections on the order of one-half inch that prior engine configurations exhibited. Prior art seal/shield configurations of the type illustrated in FIG. 1 are unusable because when large deflections occur, the flame shield members 7 and 9 separate vertically and horizontally, allowing direct exposure of the seal 1 to high temperature flames. This results in a rapid breakdown of the seal and consequent damage to the engine support structure.
In order to adequately insulate the engine support structure, it is necessary to either use larger flame shields or develop a fire seal that withstands direct exposure to flames as well as accommodates relatively large deflections between the sealed structures. Because flame shields have the disadvantage of adding more weight and complexity to the engine nacelle, as well as increasing the cost, it is desirable to eliminate them. A fire-resistant seal formed in accordance with the present invention overcomes the aforementioned disadvantages and provides a lightweight, flexible barrier that withstands direct exposure to flames.